District 9 and Alive in Joburg trailers

A summary of Alive in Joburg, from Slashfilm:

This 2005 short film portrays an alternate reality in which aliens invaded earth in 1990 and attempted to encroach on human territory and rob the planet of its resources. However, rather than coming in full-force, War of the Worlds style, the aliens allowed themselves to be subjugated and rendered second-class citizens. Themes of apartheid are unsubtly conveyed but the film is notable for its pitch-perfect documentary-style feel and its skillful use of minimal special effects.

District 9 is a full-length version of Alive in Joburg, and is in turn thought to be a test, or "proof" for an eventual production of a movie version of Halo.